In the prior art it is known to electrically connect a LED chip device to a substrate via an interconnection technique, for instance, solder bumps for flip-chips. The substrate has wiring to power the chip device, e.g. via copper wiring, vias etc. The LED device is packaged by means of a transparent resin, that provides an optical housing and protection for the LED, that can be electrically connected via electrical connectors. For optimizing the light output it is known, to provide the substrate with a reflective layer, that reflects light emitted from the LED chip device and enhances the out coupling of light out of the device. For these purposes a silver layer is usually provided. However, there are some problems with this material, which suffers from optical degradation due to silver migration and or sulphide forming etc. Also, it is a challenge to provide reflectivity for the lower wavelengths, for silver at 500 nm and lower. In addition, the material costs and process steps of current led packages are still substantial and the operational life is limited due to thermo-mechanical stresses that are induced by the bonding processes. Alternatively electric wiring is attached to the upper electrode parts of the chip (in contrast to the flip-chip technique), further giving rise to complications. In addition, there is a risk that the light extraction efficiency of light-emitting devices may be decreased by the absorption of light by such exposed portions of the wiring and electrodes.
For both variants, it is an object to provide a low cost alternative for the reflector forming, that does not suffer from the afore mentioned degradation and keeps reflective values at optimal level. Also it is an object to provide a package that has a reliable, low temperature bonding process and reduced thermo-mechanical stresses during fabrication and operational life.
JP2012-156214A discloses a light-emitting device which includes a light-emitting element that is flip-chip mounted on a substrate having a wiring, the light-emitting device being characterized in that it has an insulating light-reflecting layer disposed on the wiring and has a bump which penetrates through the insulating light-reflecting layer to reach the wiring and thereby connects the light-emitting element to the wiring.